The present invention relates generally to inverse synthetic aperture radars, and more particularly, to apparatus and methods of determining a displayable cross-range scale factor that is indicative of the relative size of objects imaged by such radars.
Electronic imaging and scanning systems, and in particular, inverse synthetic aperture radar systems, are generally discussed in "Electronic Imaging and Scanning System," Applied Optics, 16, p. 550, March 1977, and U.S. Pat. No. 4,164,788, entitled "Super-Resolution Imaging System," issued to Atul Jain. One use of air-to-ground modes of an inverse synthetic aperature radar system is for ship detection and identification. Identification of ships and other vessels contained in an inverse synthetic aperture radar (ISAR) image has not been very accurate. This is the case, because a technique for estimating cross-range scale factor has not been available. To date, no known technique for determining the cross-range scale factor of an ISAR image has been available, since the rotation rate of a target object is not a measurable quantity.
Consequently, a technique to determine a cross-scale range factor that is indicative of the relative size of objects imaged by the radar system would be an improvement in the inverse synthetic aperature radar art. Furthermore, a technique to determine the true-length of a ship or other vessel from an ISAR image would be a substantial contribution to the vessel identification art, since knowledge of true length would eliminate a substantial number of candidate ship classes in the identification process.
Accordingly, it would be an improvement in the inverse synthetic aperture radar art to have a technique for providing a cross-scale range factor that is indicative of the relative size of target objects imaged by an inverse synthetic aperture radar system.